You win some, you lose some. Divine Intervention allowed me to join a populated race on Sim Racing System today, and despite looping the car early on thanks to a last-minute gamble on aero settings – which felt like 3 clicks on the rear wing would pay off until my Ferrari fast kink prior to the bus stop – I was able to confirm something in practice that I’d been trying to pick apart and understand for a few days. While in the process of pushing the tire model in Assetto Corsa to the breaking point by trying to see how little air pressure I could keep in my tires and still remain competitive, and digging through the once-encrypted data.acd files for official Kunos content out of boredom, I ran into a little value that essentially dictates a large part of how the tires perform under stress. Third party content creators already know about this value, so it’s not a shocking revelation by any means, but it’s a value that the dedicated sim racers in Assetto Corsa should know about. It’s a straight up competitive advantage.
I’m not going to comment on the overall complexity of the tire model in Assetto Corsa, as any formula that calculates how tires heat up and cool down will simply go over my head because I’m absolutely retarded when it comes to numbers, but I do understand from shitbox racing that tires are definitely not a static entity by any means – and this remains the same throughout all forms of auto racing. Even during the course of a top-level NASCAR event, teams are always making tire pressure adjustments throughout the afternoon and well into the evening, as there’s no magic number for a tire’s peak level of grip or performance. Across the pond on European circuits, the same remains true. GT3 teams don’t show up at Paul Ricard chasing 33 PSI; it’s all about heating the tires evenly, and doing everything in your power to match inner/middle/outer temperatures across the board. Some days, it’ll be at 35 PSI. Other days, it’ll be 34, 33, or even 32. This number isn’t static. It’s a major variable, and part of what makes the technical side of auto racing so fascinating.
Assetto Corsa doesn’t swing that way. If you crack open the data.acd file of any piece of official content (or even mod cars, it doesn’t matter), and dig through the text file dedicated to the vehicle’s tires, one little line dictates the exact warm pressure where the tire provides the most grip. PRESSURE_IDEAL is the magic number you’re looking to achieve each and every time you hit the track at speed. The tire pressures you set in the garage area are what the tires are holding at room temperature. Bust open the tire app, found tucked away on the right side of the screen, and you’ll be able to see the pressure fluctuate as the tires heat up or cool down. When the tires change from a deep blue to bright green, the value listed under PRESSURE_IDEAL is what you want to show up on the heads up display.
How did I test this? I continued to fuck with running flat tires on my beloved Ferrari 488 GT3 from a few days ago, and took things into extremely obscure territory. I dropped pressures as low as they could go without the car glitching into the ground, jacked the ride height all the way up to pass tech inspection, and lastly, edited the PRESSURE_IDEAL value to the number given in-game after tire blankets had been applied, which I believe had been either 14 PSI or 16 PSI. Hitting the track with a literal monster truck Ferrari on four totally deflated racing slicks – a setup that shouldn’t work regardless of the scenario – the car had insane grip, and matched my ghost until the extremely high rolling resistance began to fuck with me at Flugplatz, the Ring’s first speed section. So this random value in the tire file was basically an on/off switch for grip. The further away you were from the magic number, the less grip you had.
And while practicing for the Sim Racing System event at Spa today, I brought things back into reality. The vanilla data.acd file had the ideal pressure sitting at 33 PSI, and upon plugging my baseline setup into the car, promptly adjusted the pressures so it would match the ideal value. Once again, it was an on/off switch. With the tires sitting at 33 PSI, I basically couldn’t get the back end to break free. Driving like a retard and heating up the rears beyond what you’d normally do under race conditions, there was a tangible decline in grip as the pressure increased to 35 and upwards with the additional heat. It’s a shame that I was retarded and took a bunch of wing out of it, because that car could have amounted to much more than a mating session with the concrete barrier.
What this means for Assetto Corsa fanboys, is that the tire model simply isn’t as realistic as Kunos claim it to be, and the unbiased individuals moaning and groaning on the forums have every right to start throwing feces at the computer monitor if continuous tire model improvements take precedence over often-requested features. However, I’ll take this article in a much different direction and instead appeal to the hardcore league guys who may not know about this. You can essentially have a massive database documenting the ideal tire pressure settings for every car in the game, and significantly cut down on the laps needed to develop a setup. Rather than spend a good chunk of time fiddling with tire pressures that you’re never quite satisfied with, there’s literally a magic number you can throw at the car and be done with it.
And finding it is pretty simple. Download the data.acd converter extension for your BMS program of choice, point the program first at the ams extension and then the car’s data file, open the tyres.ini file once the process has been completed, and find the phrase PRESSURE_IDEAL. This number is what you want the operating pressure – not the cold pressure you set in the garage menu – to achieve when your tire display is showing bright green. For example, in GT3 cars, you’ll want to hit the track with something like 21 PSI. If you’re lazy as fuck, turn on tire blankets prior to loading the session, and you won’t have to drive any laps at all.
Going through every single car in Assetto Corsa and developing a be-all, end-all tire pressure database would be insanely time consuming, so I’ve gone through just a few of the more popular classes in the game to give you guys a head start. Again, these are warm pressures, you’ll have to strap on the tire blankets and play around with cold pressures in the garage to find the corresponding warm pressure, but the entire process will take no more than ten seconds once you’re in game. And to their credit, Kunos have not adjusted this number throughout each car in a given class, nor does this value appear to change depending on the tire compound, meaning Assetto Corsa runs what could more or less be considered spec tires across the board – and for league play, that’s a good thing.
The old school DTM cars are dialed in at 38 PSI, though you’ll obviously get some crazy slides if you cook the tires even a slight amount. I assume this fairly high value is the result of the early 90’s racing slicks that didn’t quite have the technology behind them that we’re seeing in modern auto racing today.
GT4 cars, most notably the highly-popular BMW M235i, are comfortable at 33 PSI under race conditions. From Sev’s experience in the RaceDepartment league with this car, the M235i once suffered from an issue where you could drop the tire pressure as low as it would go with no detriment to your on track performance while gaining an insane amount of corner grip, and Kunos appear to have dialed this out with the current build. It would not surprise me if these are similar slicks to what you see on GT3 entries, but I’m sure someone will appear to correct me on that.
Ah, the GT3 stuff. I know the guys on Reddit will love me for this, as their ACRL series has tons of participants, so this should give the mid pack drivers a leg up on the competition. GT3 cars have the most grip with a warm pressure of 33 PSI, and in my own experience, this means setting your tires to around 21 or 22 PSI in the garage area – right on the line of what both Michelin and Pirelli advise real life owners of their tires to avoid. Once you heat up the tires and go into the 34 or 35 PSI range, the car can really step out, so those not confident in their ability to save tires over a long run should intentionally go a bit lower, maybe 18 or 19, to avoid the consequences of cooking the rear slicks.
Lastly, we get to the four GT2 cars featured in Assetto Corsa, including the P4/5 built by Scuderia Glickenhaus. GT2 as a class hasn’t existed for a few years now, and these tires appear to reflect what we saw in the 2011 American Le Mans Series season. You’ll need a slightly higher cold pressure to hit 35 PSI when out on the track, and this may be due to the weight of the car requiring a little less rolling resistance to attain a satisfactory speed – though hopefully a physics guru will step in and correct me in the next few hours. Not a whole lot of people drive these cars anymore, as they’re actually slower than the modern GT3 entries on hand, but some people really like that Corvette C7R, so this one’s for them.
How do I feel about this Ideal Pressure value? I’m glad I found it, because it turns the text files of Assetto Corsa into the answers at the back of your high school math textbook, and I can spend as much time as possible driving rather than tweaking and growing frustrated. Obviously, guys will show up and shout what they do about simulation value and whatnot, and I agree that it’s disappointing we’ve heard so much about Assetto Corsa’s constantly evolving tire model, only to discover an on/off switch that can be looked up for a tangible performance advantage, but that’s the choice Kunos made. When your game is that easy to mod, you can’t help but run into these things. I mean, it’s right there in the INI file, and you can input your own retarded values to test it yourself. A performance advantage where you don’t even have to do anything other than look for a number? I’m sold, it’s just not very simulator-like.